Zac Poonen emphasizes the ultimate defeat of Satan through Jesus' death on the cross, which liberated humanity from the bondage of fear, particularly the fear of death. He highlights that believers should never fear Satan, as God is always on their side, and that the power of Jesus' name can make the devil flee. Poonen warns against living in darkness through sin, which gives Satan power over individuals, and encourages believers to submit to God to resist the devil effectively. He reassures that Jesus' victory over Satan is a truth that should bring comfort and encouragement to all Christians. The sermon concludes with a call to live a life free from regrets by fully committing to Christ.